This invention relates to magnetic detector apparatus, such as saturable core (fluxgate) magnetic locators or gradiometers.
In magnetic detector apparatus of the type referred to, two electrically matched field-sensing elements are mounted on a non-magnetic structure such that their magnetic axes are, theoretically, precisely parallel or coaxial. The output signals of the two sensors are arranged so that they oppose each other. If the structure is oriented in any direction in a uniform magnetic field, the field components at each sensor are equal, so that there is no resulting output signal from the combination of sensors. If, however, a magnetic object exists within the detection range of the instrument, the magnetic field will generally be stronger at one of the sensors than at the other sensor, so that a net difference output signal will be produced by the combination indicative of the presence of the object. Apparatus of this type is shown, for example, in applicant's prior U.S. Pat. No. 3,961,245.
Accurate operation of detector apparatus as described is generally dependent upon substantially precise alignment of the magnetic axes of the respective sensors. While the alignment may be relatively accurately set in manufacture, the accuracy may deteriorate with use, due for example to creep in the sensor supporting structure, and while various misalignment compensation techniques are known, these can only be employed if a user has access to alignment testing equipment. Accordingly, it is clearly desirable in magnetic detector apparatus of the type described, for the sensor support structure to be constructed in a manner which can resist the tendency for misalignment to occur in the sensor magnetic axes. The present invention is concerned, inter alia, with this aspect of magnetic detector apparatus design.
The problem of possible sensor misalignment, as described above, increases with the length of the detector apparatus. (The farther apart the pair of sensors are positioned, the more accurate is the instrument.) The present invention is also concerned with the provision of sensor support structure which can maintain reasonable alignment accuracy of a pair of sensor assemblies which are significantly spaced apart, e.g., in an instrument of the order of 15 feet in length.
The invention is further concerned with a novel means for providing an electrical conducting path between the excitation conductors of a pair of sensor assemblies in magnetic detector apparatus of the type described.